Method of Manufacturing a Semiconductor Device

ABSTRACT

The quality of a non-leaded semiconductor device is to be improved. The semiconductor device comprises a sealing body for sealing a semiconductor chip with resin, a tab disposed in the interior of the sealing body, suspension leads for supporting the tab, plural leads having respective to-be-connected surfaces exposed to outer edge portions of a back surface of the sealing body, and plural wires for connecting pads formed on the semiconductor chip and the leads with each other. End portions of the suspending leads positioned in an outer periphery portion of the sealing body are not exposed to the back surface of the sealing body, but are covered with the sealing body. Therefore, stand-off portions of the suspending leads are not formed in resin molding. Accordingly, when cutting the suspending leads, corner portions of the back surface of the sealing body can be supported by a flat portion of a holder portion in a cutting die which flat portion has an area sufficiently wider than a cutting allowance of the suspending leads, whereby it is possible to prevent chipping of the resin and improve the quality of the semiconductor device (QFN).

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority from Japanese patent applicationNo. 2003-396996 filed on Nov. 27, 2003, the content of which is herebyincorporated by reference into this application.

BACKGROUND OF THE INVENTION

The present invention relates to a semiconductor device and a method ofmanufacturing the same. Particularly, the present invention is concernedwith a technique applicable effectively to improving the quality of anon-leaded semiconductor device.

In the conventional method of manufacturing a resin-sealed typesemiconductor device, a sealing sheet is brought into close contact withbottoms of at least lead portions of a lead frame with a semiconductorchip mounted thereon. The sealing sheet is a functional member forprotecting the bottoms of the lead portions lest a sealing resin shouldlap on the lead bottoms and for exposing the lead bottoms as stand-offportions of a desired value (see, for example, Patent Literature 1).

Alternatively, the sealing sheet is a functional member for protectingthe bottoms of the lead portions lest a sealing resin should lap on thelead bottoms and for exposing the lead bottoms and bottoms of landelectrodes as stand-off portions of a desired value (see, for example,Patent Literature 2).

[Patent Literature 1]

Japanese Unexamined Patent Publication No. 2001-127090 (FIG. 6)

[Patent Literature 2]

Japanese Unexamined Patent Publication No. 2002-26223 (FIG. 6)

SUMMARY OF THE INVENTION

In a non-leaded semiconductor device such as QFN (Quad Flat Non-leadedPackage), leads are partially exposed to peripheral edge portions of aback surface of a sealing body, serving as external terminals.Therefore, in resin molding, a sealing sheet is disposed on a diesurface of a resin molding die, a lead frame after pellet bonding andwire bonding is disposed on the sealing sheet, and the sealing sheet isput in close contact with a back surface (a part) of each lead. With thesealing sheet, a sealing resin is prevented from adhering to the backsurface of each lead, and by allowing each lead to sink into the sealingsheet at the time of injection of the sealing resin, each lead, afterformation of a sealing body, is slightly projected from a back surfaceof the sealing body to ensure a stand-off portion.

Stand-off portions are also formed on the side of suspension leadsdisposed at corners of the sealing body. Gate resin for resin moldingremains on surfaces (upper surfaces) of corner portions of the sealingbody in a connected state to the corner portions. Therefore, at the timeof cutting the suspension leads, it is very difficult to dispose aholder portion of a cutting die on the surfaces of the corner portions.For this reason, when cutting the suspension leads, back surfaces of thecorner portions of the sealing body are supported by the holder portionof the cutting die and in this state a cutting punch is advanced fromthe surface side of the sealing body.

At this time, since stand-off portions are also formed on the side ofsuspension leads, the cutting work is performed while the back surfacesof the corner portions are supported by a cutting die having a holdingportion of a shape (e.g., concave shape) which keeps aloof from thestand-off portions. However, when cutting the suspension leads, thesealing body present around the stand-off portions of the suspensionleads is apt to contact the holder portion of the cutting die, dependingon how variations in the state of resin molding around the stand-offportions and the holder portion of the cutting die are balanced. As aresult, when cutting the suspension leads, there arises the problem thatthe sealing body present around the stand-off portions of the suspensionleads comes into contact with the holder portion of the cutting die andcauses chipping of resin.

It is preferable that a marking step of marking the name of company anda product code on the surface side of the sealing body be carried out inthe state of multiple lead frames before cutting the suspension leads.This is advantageous to the reduction of manufacturing cost. In theforegoing lead cutting step, therefore, multiple lead frames aredisposed so that the back side of the sealing body faces up, and in themarking step, multiple lead frames are once turned upside down so thatthe surface side of the sealing body 3 faces up. When cutting thesuspension leads after the marking step, it is necessary to provide astep of again turning the multiple lead frames upside down.

Thus, there is a fear that the assembling throughput may drop, leadingto an increase of the manufacturing cost.

For example in case of mounting a semiconductor chip having the samethickness as the thickness of another semiconductor device (e.g., a thinQFP (Quad Flat Package)), a tab (chip mounting portion) and suspensionleads are formed thin by half etching so as to be within a restrictionin package height of QFN. However, the suspension leads become easier tomove because they become thinner and longer, thus giving rise to thephenomenon that the tab shifts toward the back side due to a resin flowpressure at the time of injection of resin in resin sealing.

Consequently, the tab becomes exposed to the back surface of the sealingbody or there occurs warping of the sealing body. As a result, therearise problems such as the package height becoming an off-specificationheight or the occurrence of a poor appearance.

It is an object of the present invention to provide a semiconductordevice of improved quality and a method of manufacturing the same.

It is another object of the present invention to provide a semiconductordevice improved in packaging performance and a method of manufacturingthe same.

The above and other objects and novel features of the present inventionwill become apparent from the following description and the accompanyingdrawings.

Typical modes of the present invention as disclosed herein will beoutlined below.

In one aspect of the present invention there is provided a semiconductordevice comprising a semiconductor chip having on a main surface thereofa semiconductor element and a plurality of electrodes, a sealing bodyfor sealing the semiconductor chip with resin, a chip mounting portiondisposed in the interior of the sealing body and connected to thesemiconductor chip, suspending leads for supporting the chip mountingportion, a plurality of leads exposed partially to outer edge portionsof a back surface of the sealing body and arranged side by side in theouter edge portions, and a plurality of metal thin wires for connectingthe plural electrodes of the semiconductor chip and the plural leadscorresponding thereto with each other, wherein end portions of thesuspending leads positioned in an outer periphery portion of the sealingbody are covered with the sealing body on the back surface side of thesealing body.

In another aspect of the present invention there is provided a method ofmanufacturing a semiconductor device, comprising the steps of providinga lead frame, the lead frame having a chip mounting portion, a pluralityof leads arranged around the chip mounting portion and suspending leadsfor supporting the chip mounting portion; mounting a semiconductor chiponto the chip mounting portion; connecting electrodes formed on thesemiconductor chip and the leads corresponding thereto with each otherthrough metal thin wires; disposing the lead frame onto a sealing sheetdisposed on a die surface of a resin molding die, thereafter clampingthe resin molding die in such a manner that the plural leads of the leadframe come into close contact with the sealing sheet, then sealing thesemiconductor chip and the plural metal thin wires with a sealing resinto form a sealing body in such a manner that the sealing resin isallowed to lap over back surfaces of the chip mounting portion and thesuspending leads and portions of the back surfaces of the suspendingleads corresponding to outer edge portions of the sealing body arecovered with the sealing body; and separating the leads and thesuspending leads from the lead frame.

Effects obtained by the typical modes of the present invention asdisclosed herein will be described below briefly.

Since end portions of the suspending leads positioned in the outerperiphery portion of the sealing body are covered with the sealing bodyon the side of their back surfaces, the suspending leads are not exposedto corner portions of the back surface of the sealing body and stand-offportions are not formed by the suspending leads. Consequently, whencutting the suspending leads, the corner portions of the back surface ofthe sealing body can be supported by a wide area of a flat portion of acutting die, whereby it is possible to prevent chipping of resin. As aresult, it is possible to improve the quality of the semiconductordevice produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view showing the structure of a semiconductor deviceaccording to an embodiment of the present invention;

FIG. 2 is a back view thereof;

FIG. 3 is a partial enlarged perspective view showing the structure of acorner portion of the semiconductor device of FIG. 1;

FIG. 4 is a plan view showing the structure of the semiconductor deviceof FIG. 1 as seen through a sealing body;

FIG. 5 is a sectional view showing the structure of a section takenalong line A-A in FIG. 4;

FIG. 6 is a sectional view showing the structure of a section takenalong line B-B in FIG. 4;

FIG. 7 is a sectional view showing a modification of the structure ofthe section taken along line A-A in FIG. 4;

FIG. 8 is a partial enlarged plan view showing the structure of FIG. 7as seen through the sealing body;

FIG. 9 is a partial enlarged back view showing an example of pin arrayon a back surface of a corner portion of the semiconductor device ofFIG. 1;

FIG. 10 is a back view showing the structure of a semiconductor deviceaccording to a modification of the embodiment of the present invention;

FIG. 11 is an assembling flow chart showing an example of a method ofmanufacturing the semiconductor device of FIG. 1;

FIG. 12 is a partial sectional view showing an example of a resininjecting method using a plate thickness gate in a molding step in thesemiconductor device manufacturing method shown in FIG. 11;

FIG. 13 is a partial sectional view showing an example of a resininjecting method using an ordinary gate in the molding step in thesemiconductor device manufacturing method shown in FIG. 11;

FIG. 14 is a partial enlarged plan view showing an example of apositional relation between a gate and leads in case of using the platethickness gate shown in FIG. 12;

FIG. 15 is a partial enlarged plan view showing an example of apositional relation between a gate and leads in case of using theordinary gate shown in FIG. 13;

FIG. 16 is a partial enlarged plan view showing the structure of a framecorner portion shown in FIG. 15;

FIG. 17 comprises partial enlarged sectional views and a partialenlarged side view, showing an example of machining states inmanufacturing steps from lead cutting to dividing into individual piecesin the semiconductor device manufacturing method shown in FIG. 11;

FIG. 18 is a partial enlarged back view showing an example of pin arrayon a back surface of a corner portion of the semiconductor device ofFIG. 1; and

FIG. 19 is a partial enlarged perspective view showing the structure ofa corner portion of the semiconductor device in case of using theordinary gate shown in FIG. 13.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following embodiments, as to the same or similar portions,repeated explanations thereof will be omitted in principle except whererequired.

Where required for convenience' sake, the following embodiments willeach be described in a divided manner into plural sections orembodiments, but unless otherwise mentioned, they are not unrelated toeach other, but are in a relation such that one is a modification, adetailed description, or a supplementary explanation, of part or thewhole of the other.

In the following embodiments, when reference is made to the number ofelements (including the number, numerical value, quantity, and range),no limitation is made to the number referred to, but numerals above andbelow the number referred to will do as well unless otherwise mentionedand except the case where it is basically evident that limitation ismade to the number referred to.

Embodiments of the present invention will be described in detailhereinunder with reference to the accompanying drawings. In all of thedrawings for explaining the embodiments, members having the samefunctions are identified by the same reference numerals, and repeatedexplanations thereof will be omitted in the following description.

EMBODIMENTS

FIG. 1 is a plan view showing the structure of a semiconductor deviceaccording to an embodiment of the present invention, FIG. 2 is a backview thereof, FIG. 3 is a partial enlarged perspective view showing thestructure of a corner portion of the semiconductor device of FIG. 1,FIG. 4 is a plan view showing the structure of the semiconductor deviceof FIG. 1 as seen through a sealing body, FIG. 5 is a sectional viewshowing the structure of a section taken along line A-A in FIG. 4, FIG.6 is a sectional view showing the structure of a section taken alongline B-B in FIG. 4, FIG. 7 is a sectional view showing a modification ofthe structure of the section taken along line A-A in FIG. 4, FIG. 8 is apartial enlarged plan view showing the structure of FIG. 7 as seenthrough the sealing body, FIG. 9 is a partial enlarged back view showingan example of pin array on a back surface of a corner portion of thesemiconductor device of FIG. 1, FIG. 10 is a back view showing thestructure of a semiconductor device according to a modification of theembodiment of the present invention, FIG. 11 is an assembling flow chartshowing an example of a method of manufacturing the semiconductor deviceof FIG. 1, FIG. 12 is a partial sectional view showing an example of aresin injecting method using a plate thickness gate in a molding step inthe semiconductor device manufacturing method shown in FIG. 11, FIG. 13is a partial sectional view showing an example of a resin injectingmethod using an ordinary gate in the molding step in the semiconductordevice manufacturing method shown in FIG. 11, FIG. 14 is a partialenlarged plan view showing an example of a positional relation between agate and leads in case of using the plate thickness gate shown in FIG.12, FIG. 15 is a partial enlarged plan view showing an example of apositional relation between a gate and leads in case of using theordinary gate shown in FIG. 13, FIG. 16 is a partial enlarged plan viewshowing the structure of a frame corner portion shown in FIG. 15, FIG.17 comprises partial enlarged sectional views and a partial enlargedside view, showing an example of machining states in manufacturing stepsfrom lead cutting to dividing into individual pieces in thesemiconductor device manufacturing method shown in FIG. 11, FIG. 18 is apartial enlarged back view showing an example of pin array on a backsurface of a corner portion of the semiconductor device of FIG. 1, andFIG. 19 is a partial enlarged perspective view showing the structure ofa corner portion of the semiconductor device in case of using theordinary gates shown in FIG. 13.

The semiconductor device according to the embodiment shown in FIGS. 1 to6 is a small-sized, non-leaded semiconductor device in which pluralleads 1 a are arranged side by side in outer edge portions of a backsurface 3 a of a sealing body 3. Reference is made to QFN 5 as anexample of the semiconductor device of this embodiment.

The QFN 5 comprises a semiconductor chip 2, the semiconductor chip 2having on a main surface 2 b thereof a semiconductor element and pluralpads (electrodes) 2 a, a sealing body 3 for sealing the semiconductorchip 2 with resin, a tab 1 b as a chip mounting portion connected to thesemiconductor chip 2, the tab 1 b being disposed in the interior of thesealing body 3, suspending leads 1 e connected to the tab 1 b at cornerportions of the tab to support the tab, plural leads 1 a arranged sideby side in outer edge portions of a back surface 3 a of the sealing body3, the leads 1 a having respective to-be-connected surfaces (each beinga part of each lead) which are exposed to the said outer edge portions,and plural wires (metal thin wires) 4 for connection between the pluralpads 2 a formed on the semiconductor chip 2 and the plural leads 1 acorresponding thereto. End portions of the suspending leads 1 epositioned in an outer periphery portion of the sealing body 3 arecovered with the sealing body 3 on the back surface 3 a of the sealingbody.

That is, as shown in FIG. 2, end portions of the suspending leads 1 eare not exposed to corner portions of the back surface 3 a of thesealing body 3, but are embedded in the interior of the sealing body 3.However, at each of the corner portions of the sealing body 3, a cutface 1 h of each suspending lead 1 e is exposed to a side face of thecorner portion, as shown in FIG. 3.

Thus, the end portions of the suspending leads 1 e positioned in theouter periphery portion of the sealing body 3 are covered with thesealing body 3 on their back surfaces if and are not exposed to thecorner portions of the back surface 3 a of the sealing body 3. Accordingto this structure, stand-off portions of the suspending leads 1 e(projecting portions of the leads from the back surface 3 a of thesealing body 3) are not formed by resin molding. Consequently, whencutting the suspending leads, as shown in FIG. 17, the corner portionsof the back surface 3 a of the sealing body 3 can be supported by a flatportion 10 c of a holder portion 10 a of a cutting die, the flat portion10 c having an area wider than a cutting allowance 1 m of eachsuspending lead 1 e. As a result, it is possible to prevent the chippingof resin.

In the QFN 5 of this embodiment, the tab 1 b and the suspending leads 1e for supporting the tab are formed thin by half etching for example andare embedded in the interior of the sealing body 3, as shown in FIG. 5.However, projecting portions 1 j are formed on back surfaces 1 d and 1 fof the tab 1 b and the suspending leads 1 e, respectively, and areexposed to the tack surface 3 a of the sealing body 3.

The method for thinning the tab and the suspension leads 1 e is notlimited to half etching, but there may be adopted any other method thanhalf etching, such as coining for example. In the QFN 5 of thisembodiment, the tab 1 b and the suspending leads 1 e are formed byhalf-etching the other area than the areas corresponding to theirprojecting portions 1 j in the stage of fabricating the lead frame 1(see FIG. 12). The areas which have not been subjected to half etchingserve as the projecting portions 1 j.

Since the projecting portions 1 j are thus formed on the back surfaces 1d and 1 f of the tab 1 b and the suspending leads 1 e, even if the tab 1b and the suspension leads 1 e are pushed toward the back surfaces underthe resin flow pressure at the time of resin injection in resin sealing,the projecting portions 1 j come into contact with a film sheet (sealingsheet) 8 on a die surface 9 d of a resin molding die 9, as shown in FIG.12, whereby the tab 1 b and the suspending leads 1 e are supported bythe projecting portions 1 j and no longer shift toward the backsurfaces. Thus, it is possible to prevent shifting of the tab 1 b towardits back surface under the resin flow pressure.

Since the projecting portion 1 j on the tab 1 b is for supporting thetab 1 b at the time of resin injection to prevent the tab from shiftingto its back surface side, it is preferable that the projecting portion 1j on the tab be formed centrally of the back surface 1 d of the tab 1 b,as shown in FIGS. 5 and 6. Plural other projecting portions 1 j may beprovided around the central projecting portion 1 j. However, it ispreferable to avoid such arrangement of other projecting portions 1 jbecause wiring is distributed in a layer which underlies the backsurface 1 d of the tab 1 b. As to the tab 1 b, it is optional whether alarge tab 1 b having an area larger than the area of the semiconductorchip 2 is to be used or a small tab 1 b having an area smaller than thearea of the semiconductor chip 2 is to be used. However, by making areaof the tab 1 b smaller than that of the semiconductor chip 2, peeling insolder reflow is prevented and stress in temperature cycle isdiminished, so that the packaging reliability is improved.

As to the suspending leads 1 e, as shown for example in a modificationof FIGS. 7 and 8, it is preferable that projecting portions 1 j beformed on the back surfaces 1 f of the suspending leads at positionscorresponding to the corner portions of the semiconductor chip 2. Whenin addition to those projecting portion 1 j there is formed a projectingportion 1 j centrally of the back surface 1 d of the tab 1 b, it followsthat projecting portions 1 j are exposed at five positions on the backsurface 3 a of the sealing body 3, as shown in FIG. 2.

Consequently, it is possible to stabilize the location of the tab 1 band prevent tilting of the tab 1 b itself.

When the number of pins increases in a multi-pin structure, thepin-to-pin pitch tends to become narrower, so from the standpoint of pinarray it is preferable that the suspending leads 1 e be not exposed atthe corner portions on the back surface 3 a of the sealing body 1. Forexample, in the case of QFN 5 having a package size of 9 mm×9 mm and 64pins, and given that the pin-to-pin pitch is A, the pin-to-pin distanceat a corner portion is B, and the length of a to-be-connected surface asan exposed portion of each lead 1 a is C, as shown in FIG. 9, it ispreferable to determine those sizes so as to satisfy the relation ofA>B>C. Also in this case it is effective to adopt the QFN structure ofthis embodiment wherein the suspending leads 1 e are embedded in theinterior of the sealing body 3 at corner portions. As shown in FIG. 18,as the package size becomes smaller with consequent increase in thenumber of pins and narrowing of the pin-to-pin pitch, the pin-to-pindistance B at each corner portion becomes shorter and therefore it ispreferable that suspending lead 1 e-side corners of leads 1 a located ateach corner portion of the back surface 3 a of the sealing body 3 betapered (chamfered) as indicated at 1 n.

In the QFN 5 of this embodiment, the tab 1 b and the suspending leads 1e need not always be provided with projecting portions 1 j, and theremay be adopted a structure wherein the tab and the suspending leads 1 eare not exposed at all to the back surface 3 a of the sealing body 3, asshown in a modification of FIG. 10. According to this structure, theback surfaces 1 d and 1 f of the tab 1 b and the suspending leads 1 eare formed thin by half etching and the projecting portions 1 j are notprovided. Also in this case, since the suspending leads 1 e are notexposed to the corner portions of the back surface 3 a of the sealingbody 3, so that it is possible to prevent chipping of resin when cuttingthe suspending leads.

In the QFN 5 of this embodiment, as described above, since end portionsof the suspending leads 1 e located in the outer periphery portion ofthe sealing body 3 are covered with the sealing body on the backsurfaces 1 f of the suspending leads, the suspending leads 1 e are notexposed to the corner portions of the back surface 3 a of the sealingbody 3 and therefore stand-off portions are not formed by the suspendingleads 1 e. Consequently, when cutting the suspending leads, as shown inFIG. 17, the corner portions of the back surface 3 a of the sealing body3 are supported by the flat portion 10 c of the holder portion 10 a ofthe cutting die 10 which flat portion 10 c has a wider area than thecutting allowance 1 m of each suspending lead 1 e, whereby it ispossible to prevent chipping of resin.

As a result, it is possible to improve the quality of QFN 5.

Moreover, since the suspending leads 1 e are not exposed to the cornerportions of the back surface 3 a of the sealing body 3, in a packagingsubstrate for packaging the QFN 5, wiring can be distributed in areascorresponding to the corner portions of the back surface 3 a of thesealing body 3 and hence it is possible to improve the packagingperformance of the QFN 5.

Besides, the projecting portions 1 j are provided on at least one orboth of the back surface 1 d of the tab 1 b and the back surfaces 1 f ofthe suspending leads 1 e, so even if the tab 1 b and the suspendingleads 1 e are pushed toward the back surfaces of the tab 1 b and thesuspending leads 1 e by the resin flow pressure at the time of resininjection in resin sealing, the projecting portions 1 j come intocontact with the film sheet 8 on the die surface 9 d of the resinmolding die 9 to support the tab 1 b and the suspending leads 1 e, asshown in FIG. 12.

Thus, the tab 1 b and the suspending leads 1 e are supported by theprojecting portions 1 j and no longer shift toward their back surfaces,so that it is possible to prevent shifting of the tab 1 b toward itsback surface under the resin flow pressure. Consequently, exposure tothe back surface 1 d of the tab 1 b and warping of the sealing body 3can be prevented. Further, it is possible to prevent the height of QFN 5from becoming an off-specification height or prevent the occurrence of apoor appearance, whereby the quality of QFN 5 can be improved.

As shown in FIG. 12, the semiconductor chip 2 is fixed onto a chipsupporting surface 1 c of the tab 1 b through a die bonding material(e.g., silver paste) 6. A back surface 2 c of the semiconductor chip 2and the chip supporting surface 1 c of the tab 1 b are connected witheach other.

As shown in FIG. 6, the leads 1 a arranged side by side in outer edgeportions of the back surface 3 a of the sealing body 3 in QFN 5 eachhave a thick-walled portion 1 i, a part of which is exposed as ato-be-connected surface 1 g to the back surface 3 a of the sealing body3. An exterior plating such as solder plating or palladium plating isapplied to the to-be-connected surface 1 g.

The tab 1 b, suspending leads 1 e and leads 1 a are each formed by athin plate such as a thin copper alloy plate for example.

To match the thinning of the QFN 5, the back surface 2 c of thesemiconductor chip 2 is subjected to back grinding to a chip thicknessof, for example, 0.2 mm (200 μm).

The wires 4 as metal thin wires for connecting the pads 2 a of thesemiconductor chip 2 and the corresponding leads 1 a with each otherare, for example, gold wires.

The sealing body 3 is formed by resin sealing in accordance with themolding method. The sealing resin used is, for example, a thermosettingepoxy resin.

Next, a description will be given below of a method of manufacturing theQFN 5 (semiconductor device) of this embodiment with reference to theassembling flow shown in FIG. 11.

In the case where the QFN 5 is fabricated to match the thinningtendency, a back surface of a semiconductor wafer is subjected to backgrinding to thin the wafer in step S1. For example, the back grinding isperformed so that the wafer thickness becomes 200 μm. However, the backgrinding for the semiconductor wafer for the reduction of thickness isnot always required.

On the other hand, a lead frame 1 is provided. The lead frame 1 has atab 1 b on which a semiconductor chip 2 can be mounted, plural leads 1 aarranged around the tab 1 b, and suspending leads 1 e for supporting thetab 1 b. Back surfaces 1 d and 1 f of the tab 1 b and the suspendingleads 1 e are formed thin by half etching for example and arerespectively provided with projecting portions 1 j.

Thereafter, die bonding is performed in step S2. In this die bondingstep, the semiconductor chip 2 is fixed through a die bonding material 6to a chip supporting surface 1 c of the tab 1 b which is a chip mountingportion of the lead frame 1.

Subsequently, wire bonding is performed in step S3. In this wire bondingstep, pads 2 a on the semiconductor chip 2 and the corresponding leads 1a are connected together through wires (metal thin wires) 4 such as goldwires.

Then, resin sealing (molding) is performed in step S4. First, as shownin FIG. 12, a film sheet 8 as a sealing sheet is disposed onto a diesurface 9 d of a lower die 9 b in a resin molding die 9. Further, thelead frame 1 is disposed onto the film sheet 8 and thereafter the resinmolding die 9 is clamped so that to-be-connected surfaces 1 g of theplural leads 1 a come into close contact with the film sheet 8.

Subsequently, a sealing resin is allowed to lap on the back surfaces 1 dand 1 f of the tab 1 b and the suspending leads 1 e, and thesemiconductor chip 2 and the plural wires 4 are sealed with the resin sothat the back surface 1 d of the tab 1 b and the back surfaces 1 f ofthe portions of the suspending leads 1 e corresponding to outer edgeportions of a sealing body 3, i.e., the back surfaces 1 f of endportions of the suspending leads 1 e, are covered with the sealing body(sealing resin), to form the sealing body 3.

When injecting the sealing resin into a cavity 9 c formed in an upperdie 9 a of the resin molding die 9, as shown in FIG. 14, a portion ofeach suspending lead 1 e not subjected to half etching and locatedoutside an outer half-etched area (hatched area P in FIG. 14) of an endportion of each suspending lead 1 e is pushed down by a gate portion 9 eof the resin molding die 9. In this state, the sealing resin is injectedinto the cavity 9 c from gaps 1 k each corresponding to the leadthickness and formed on both sides of each suspending lead 1 e as inFIG. 14 through a resin injection path 7 extending from a runner 9 f tothe cavity 9 c through the gate portion 9 e in FIG. 12, to perform resinsealing.

In this case, since each suspending lead 1 e is formed thin by halfetching, the gate opening expands and hence it is possible to improvethe fluidity of the sealing resin flowing into the cavity 9 c.

Further, as shown in FIG. 12, since projecting portion 1 j are formed onthe back surface 1 d of the tab 1 b and the back surfaces 1 f of thesuspending leads 1 e, even when the tab 1 b and the suspending leads 1 eare pushed toward their back surfaces under the resin flow pressure atthe time of resin injection, the projecting portions 1 j come intocontact with the film sheet 8 provided on the die surface 9 d of thelower die 9 b in the resin molding die 9. As a result, the tab 1 b andthe suspending leads 1 e are supported by the projecting portions 1 jand do not shift toward their back surfaces, whereby the tab 1 b can beprevented from shifting toward its back surface under the resin flowpressure.

Consequently, exposure to the back surface 1 d of the tab 1 b andwarping of the sealing body 3 can be prevented. Further, it is possibleto prevent the height of QFN 5 from becoming an off-specification heightor prevent the occurrence of a poor appearance. Thus, the quality of QFN5 can be improved.

As shown in a modified example of FIGS. 13 and 15, the gate opening maybe disposed above the suspending leads 1 e to form such a resininjection path 7 as shown in FIG. 13. Also in this case, since the gateopening expands, it is possible to improve the fluidity of the sealingresin flowing into the cavity 9 c. In this resin injecting method usingthe ordinary gate, as shown in FIG. 19, a resin burr 3 b is formed onthe surface side of each suspending lead 1 e after the end of resinmolding. When cutting each suspending lead 1 e, therefore, the backsurfaces of the corner portions of the sealing body 3 are supported by acutting die 10 and in this state a cutting punch 10 d is advanced fromthe surface side (upper side) of the sealing body 3 to cut thesuspending lead 1 e.

Therefore, the cutting of each suspending lead 1 e can be done using thecutting die 10 provided with a holding portion 10 a of a flat surface(flat portion 10 c) without forming a concave groove for escape from theresin burr 3 b in the holder portion 10 a of the cutting die (see FIG.17).

FIG. 16 shows a positional relation between an outer periphery line ofthe sealing body 3 defined when sealing is performed by this resininjecting method and a half etching area P (hatched area P in FIGS. 15and 16) of each suspending lead 1 e. Since the half etching area P ofthe suspending lead 1 e extends to both inside and outside of a cornerportion of the sealing body 3, it is possible to realize the structurewherein the back surfaces 1 f of end portions of the suspending leads 1e are covered with the sealing body 3 (sealing resin).

Thus, since the suspending leads 1 e are not exposed to the cornerportions of the back surfaces 3 a of the sealing body 3, stand-offportions are not formed by the suspending leads 1 e.

However, since the resin molding is carried out in a state in which theto-be-connected surfaces 1 g of the plural leads 1 a other than thesuspending leads 1 e are put in close contact with the film sheet 8 andare allowed to slightly sink into the film sheet 8, the to-be-connectedsurfaces 1 g of the leads 1 a can be projected from the back surface 3 aof the sealing body 3 after resin sealing and it is possible to form astand-off portion in each lead 1 a.

After the end of resin sealing, lead cutting is performed in step S5shown in FIG. 11.

In this lead cutting step, as shown in step S5 in FIG. 17, cuttingallowances 1 m of the leads 1 a are sandwiched and fixed in betweenholder portions 10 a and presser portions 10 b of the cutting die 10while the back surface 3 a of the sealing body 3 is allowed to face up.In this state, the cutting punch 10 d is advanced from the back surface3 a side (above side) of the sealing body 3 to cut the plural leads 1 a.

That is, each lead 1 a is formed with a stand-off portion on the backsurface 3 a side of the sealing body 3 and it is preferable that a leadburr formed on the cut surface of each lead be formed on the surfaceside of each lead. When cutting the leads, therefore, it is not that theto-be-connected surface 1 g as the back surface of each lead 1 a isheld, but the surface side of each lead is held, and in this state thecutting punch 10 d is advanced from the back side (from above) of theleads 1 a to cut the leads.

As a result, a lead burr formed on the cut surface of each lead 1 a canbe formed so as to face the surface side of each lead, whereby when theQFN 5 is soldered to a packaging substrate, it is possible to increasethe soldering area.

Thereafter, the manufacturing flow shifts to a marking step S6 shown inFIG. 11. In this marking step, as shown in FIG. 17, first the sealingbody 3 is turned upside down so that the surface side of the sealingbody 3 faces up. In this state, a desired marking is performed from thesurface side of the sealing body 3 by applying, for example, a laserbeam 11 to the surface of the sealing body.

Thereafter, the manufacturing flow shifts to a step of dividing intoindividual pieces shown as step S7 in FIG. 11. In this step, as shown instep S7 in FIG. 17, while allowing the surface of the sealing body 3 toface up, the cutting punch 10 d is advanced from the surface side of thesealing body 3 to cut the leads 1 e for division into individual pieces.That is, in the QFN 5 of this embodiment, the suspending leads 1 e arenot formed with stand-off portions, so when cutting the suspendingleads, outer edge portions of the back surface 3 a of the sealing body 3corresponding to end portions of the suspending leads 1 e can besupported by the flat portion 10 c of the holder portion 10 a in thecutting die 10 which flat portion 10 c has an area sufficiently widerthan the cutting allowance 1 m of each suspending lead 1 e. In thisstate it is possible to cut the suspending leads.

Consequently, the inverting step which is performed in the use of theplate thickness gate can be omitted and it is possible to prevent theoccurrence of resin chipping when cutting the suspending leads in theuse of the ordinary gate, whereby the quality of QFN 5 can be improved.

Thus, in assembling the QFN 5 of this embodiment, both marking step andthe step of dividing into individual pieces (cutting the suspendingleads) can be carried out in a state in which the surface side of thesealing body 3 faces up. Besides, the inverting step of inverting thesealing body 3 so as to let the back surface of the sealing body face upcan be omitted. Therefore, it is also possible to use a continuousprocessing apparatus which can perform both marking operation andsuspending lead cutting operation. As a result, it becomes possible toreduce the manufacturing cost.

In the suspending lead cutting step, irrespective of whether the markingstep is used or not, the effect of preventing the chipping of resin canbe attained by advancing the cutting punch 10 d from the surface side ofthe sealing body 3. However, even if the cutting punch 10 d is advancedfrom the back surface 3 a side of the sealing body 3, it is possible toobtain the effect of diminishing the chipping of resin. Therefore, inthe case where the marking step is not carried out or is carried outafter dividing into individual QFNs 5, the lead cutting and suspendinglead cutting step may be carried out while allowing the back surface 3 aof the sealing body 3 to face up.

The dividing step by cutting suspending leads is followed by storageshown in step S8 in FIG. 11 to store the QFN 5 in a tray (or amagazine). The procedure may be changed such that the lead cutting andsuspending lead cutting step is preceded by the marking step, and aftercompletion of the dividing step, the manufacturing flow shifts tostorage shown in step S8 in FIG. 11. However, when the marking step iscarried out before the lead cutting step, there is a fear that the markmay be scratched or vanish in washing after the cutting of leads.

Although the present invention has been described above on the basis ofembodiments thereof, it goes without saying that the present inventionis not limited to the above embodiments, but that various changes may bemade within the scope not departing from the gist of the invention.

For example, although reference has been made in the above, embodimentsto QFN 5 as an example of the semiconductor device according to thepresent invention, the semiconductor device may be any othersemiconductor device than QFN insofar as it is a non-leaded type of astructure wherein end portions of suspending leads 1 e are not exposedto corner portions of the back surface 3 a of the sealing body 3.

The present invention is suitable for the technique of manufacturingelectronic devices and semiconductor devices.

1. A semiconductor device comprising: a semiconductor chip having a mainsurface, a back surface, a semiconductor element and a plurality ofelectrodes, the semiconductor element and the plural electrodes beingformed over the main surface of the semiconductor chip; a sealing bodyfor sealing the semiconductor chip with resin; a chip mounting portiondisposed in the interior of the sealing body and connected to thesemiconductor chip; suspending leads for supporting the chip mountingportion; a plurality of leads exposed partially to outer edge portionsof a back surface of the sealing body and arranged side by side in theouter edge portions; and a plurality of wires for connecting the pluralelectrodes of the semiconductor chip and the plural leads correspondingthereto with each other, wherein end portions of the suspending leadspositioned in an outer periphery portion of the sealing body are coveredwith the sealing body on the back surface side of the sealing body.
 2. Asemiconductor device according to claim 1, wherein a projecting portionis formed over a back surface opposite to the chip mounting side of thechip mounting portion, the projecting portion being exposed to the backsurface of the sealing body.
 3. A semiconductor device according toclaim 1, wherein projecting portions are formed over back surfacesopposite to the chip mounting side of the suspending leads, theprojecting portions being exposed to the back surface of the sealingbody.
 4. A semiconductor device according to claim 1, wherein aprojecting portion is formed centrally of a back surface opposite to thechip mounting side of the chip mounting portion, and projecting portionsare formed over back surfaces opposite to the chip mounting side of thesuspending leads, the projecting portions of the chip mounting portionand the suspending leads being exposed to the back surface of thesealing body.
 5. A semiconductor device according to claim 1, wherein aprojecting portion is formed over a back surface opposite to the chipmounting side of the chip mounting portion, and projecting portions areformed over back surfaces opposite to the chip mounting side of thesuspending leads at positions corresponding to corner portions of thesemiconductor chip, the projecting portions of the chip mounting portionand the suspending leads being opposed to the back surface of thesealing body.
 6. A semiconductor device according to claim 1, wherein aplurality of projecting portions are formed over a back surface oppositeto the chip mounting side of the chip mounting portion, and projectingportions are formed over back surfaces opposite to the chip mountingside of the suspending leads, the projecting portions of the chipmounting portion and the suspending leads being exposed to the backsurface of the sealing body.
 7. A semiconductor device according toclaim 6, wherein the chip mounting portion and the suspending leads arehalf-etched in other areas than the respective projecting portions.
 8. Asemiconductor device according to claim 1, wherein back surfacesopposite to the chip mounting side of the suspending leads are coveredwith the sealing body and not exposed to the back surface of the sealingbody.
 9. A semiconductor device according to claim 1, wherein the areaof the chip mounting portion is smaller than the area of thesemiconductor chip.
 10. A method of manufacturing a semiconductordevice, comprising the steps of: (a) providing a lead frame, the leadframe including a chip mounting portion, a plurality of leads arrangedaround the chip mounting portion, and suspending leads for supportingthe chip mounting portion; (b) mounting a semiconductor chip over thechip mounting portion; (c) connecting electrodes formed over thesemiconductor chip and the leads corresponding thereto with each otherthrough wires; (d) disposing the lead frame over a sealing sheetdisposed over a die surface of a resin molding die, thereafter clampingthe resin molding die in such a manner that the plural leads of the leadframe come into close contact with the sealing sheet, then sealing thesemiconductor chip and the wires with a sealing resin to form a sealingbody in such a manner that the sealing resin is allowed to lap over backsurfaces of the chip mounting portion and the suspending leads andportions of the back surfaces of the suspending leads corresponding toouter edge portions of the sealing body are covered with the sealingbody; and (e) separating the leads and the suspending leads from thelead frame.
 11. A method according to claim 10, wherein the sealing withthe sealing resin is carried out by injecting the sealing resin into acavity of the resin molding die in the step (d) in such a manner thatthe sealing resin is injected into the cavity through gaps eachcorresponding to the thickness of each of the leads and formed on bothsides of each of the suspending leads while pressing down the outside ofan end portion of the suspending lead by a gate portion of the resinmolding die.
 12. (canceled)
 13. (canceled)
 14. A semiconductor devicecomprising: a lead frame, the lead frame including a chip mountingportion, suspending leads connected to the chip mounting portion, and aplurality of leads arranged around the chip mounting portion; asemiconductor chip disposed over the chip mounting portion, thesemiconductor chip including a plurality of semiconductor elements and aplurality of electrodes; a plurality of wires for electricallyconnecting the plural electrodes of the semiconductor chip and theplural leads with each other; and a resin body for sealing thesemiconductor chip, the chip mounting portion, the plural wires and theplural leads, the resin body having a surface, a back surface oppositeto the surface and side faces located between the surface and the backsurface; wherein one end portions of the plural leads are exposed fromthe back surface of the resin body, wherein at the side faces of theresin body the plural leads and the suspending leads have cut surfacescreated by cutting the lead frame, and wherein the cut surfaces of thesuspending leads do not reach the back surface of the resin body.
 15. Asemiconductor device according to claim 14, wherein the length of thecut surface of each of the suspending leads in the thickness directionof the resin body is shorter than the length of the cut surface of eachof the plural leads in the thickness direction of the resin body.